We do, in fact, know what it would cost to extract the heat in usable form. And that would be enormously more costly than what we do with fission. Extracting a

We do, in fact, know what it would cost to extract the heat in usable form. And that would be enormously more costly than what we do with fission. Extracting a few grams of tritium or helium-3, at a few parts per billion, from a thousand tons of molten, radioactive lithium every day, for fuel, can be no picnic. We can anyway be glad most of the lithium itself is not radioactive, just metal impurities spalled from surfaces of the pipes it ran in. Decommissioning would necessarily be at least as big a job as a regular nuke, because the whole reactor, thousands of tons of embrittled metal, would have been blasted with hot neutrons for months or years. A good home for a thousand tons of what was molten neutron-irradiated lithium is no easier to find than for spent uranium.